The invention relates generally to packaging for food products, and more particularly to zipper-equipped reclosable pouches and methods and apparatus for forming, filling and sealing such pouches.
In providing a commercially viable zipper-equipped package, among the considerations that must be addressed are ease of use and economy of manufacture. It is desirable that the package be capable of being formed, filled and sealed at high throughput rates. Additionally, the package must be durable to withstand the stresses of the form/fill/seal operation and subsequent shipping and handling without damage and without deterioration of appearance.
When handling products comprised of numerous small pieces such as shredded cheese, cereal, etc., the package maybe partly formed into an open-topped pouch, and product may be dispensed into the partially-formed pouch through the open top. One approach is to employ a vertical form/fill/seal system, an example of which is shown in U.S. Pat. No. 4,874,257, with the zipper being disposed vertically along one side of the package being formed, and the pouch being filled by gravity-induced flow of product downward from a filling spout. Another approach is illustrated by U.S. Pat. No. 5,519,982, in which the pouches travel horizontally as they are formed, filled and sealed.
In zipper-equipped package, where the ends of the zippers extend into seal areas, difficulty may be encountered in providing seals at high throughput rates, due to the increased thickness of the seal area at the ends of the zipper. Another problem is that opening and reclosing zippers may be difficult for the consumer, even where gripper beads are provided, as discussed in, e.g., U.S. Pat. No. 5,519,982.
To address the latter problem, a slider may be provided in conjunction with the zipper strips. Sliders that may be moved linearly to force the profiles together or apart are well known in the art. However, installation of the slider complicates the manufacturing process. Also, the slider may tend to split the joint between the package walls at the ends of the zipper track, requiring that stops be provided, which further complicates the manufacturing process. Various stop designs are shown in, e.g., U.S. Pat. Nos. 5,833,791; 5,405,478; 5,067,208; 5,448,807; and 5,442,837. U.S. Pat. No. 5,211,482 describes post-filling application of a zipper closure that includes a slider.
There is a continuing need for improved packages of the type described above, and for improved form/fill/seal operations for such packages which address the aforementioned considerations while avoiding the disadvantages of the prior art.
The invention provides a novel method and apparatus for providing a slider-equipped zipper fastener on a pouch in a form/fill/seal operation.
In the preferred embodiment of the invention, a foldable slider is employed, and is shifted from an open configuration to a closed configuration during installation on zipper strips on the pouch. Integral stops are preferably formed from the zipper material by application of heat and pressure to the ends of the zipper, without requiring installation of separate, discrete components.
A hermetic peelable seal preferably is provided beneath the zipper strips. The slider preferably is applied to the zipper strips immediately before or immediately after filling, or immediately after formation of the peelable seal.
The slider may include means to secure it in closed position on the zipper strips by a mechanical locking mechanism such as a snap fit engagement, or the slider may be welded in closed position by application of heat, or by ultrasonic welding.
An opening mechanism may be employed to separate the walls of the pouch to a predetermined position relative to one another while positioning and closing the slider. The opening mechanism may employ vacuum cups to engage the walls of the pouch.
The zipper strips are in an open position as the slider is installed. After installation of the slider on the zipper, the slider may be moved along the zipper to close the zipper.
The method and apparatus of the invention may be employed in conjunction with packaging of various food products, including but not limited to, e.g., cheese products in shredded, sliced or chunk form, sliced meats, and other food products packaged for retail sale.